1. Field of the Invention
The present invention relates to an activated carbon, a process for producing the activated carbon and adsorption using the activated carbon.
2. Description of the Related Art
Activated carbon is a porous carbonaceous substance having a large specific surface area and large adsorption ability and has a wide range of uses as an adsorbent for various purposes.
Activated carbon can be used for adsorbing gases and vapors, recovering solvents, purifying gases, deodorizing gases, and contacting with liquids so as to treat water, decolor or purify solutions. Further, activated carbon can be used as carriers for catalysts.
Heretofore, activated carbon has been manufactured by treating wood or brown coal with an activating agent, e.g. zinc chloride, phosphoric acid and the like followed by dry distillation, or by activating charcoal with steam. For example, charcoal, coconut husk, coal char and the like are sufficiently carbonized followed by a high temperature treatment by means of steam. Or the activated carbon is activated by soaking in zinc chloride and calcination at a high temperature.
Activated carbon usually has specific surface area of 800-1200 m.sup.2 /g, pore volume of 0.2-2 cm.sup.3 /g and pore size of 1-4 nm.
Activated carbon is comprised of mainly carbon and small amounts of hydrogen, oxygen and inorganic components. With respect to the chemical structure, activated carbon is mainly composed of graphite, amorphous and has functional groups such as hydroxy group, quinone group and the like on the surface.
According to the present invention, it is contemplated to produce an activated carbon of excellent adsorbability by using waste tires which have recently caused difficult problems as to disposal, in place of ordinary starting materials such as charcoal, brown coal, coconut husk, coal char and the like. Further it is contemplated to use particular properties of the activated carbon effectively.
Japanese Patent Application Laid-open No. Hei 1-127812 discloses that waste tires are burned as a fuel for boilers and the resulting cinder adsorbs perchloroethylene gas to some extent.
Exhaust gas from combustion of heavy oil, such as from heavy oil combustion boilers, contains sulfur oxide (SO.sub.2) and nitrogen oxides (Nox) which cause acidic rain, and therefore SO.sub.2 and Nox should be removed from the exhaust gas. Heretofore, removal of these harmful components has been carried out as shown below.
In coal thermoelectric power plants, coal cinders are mixed with quick lime and gypsum and the resulting mixture is used for adsorbing SO.sub.2 in the exhaust gas.
This mixture material is a product solidified with pitch.
In coal combustion boilers and heavy oil combustion boilers, 99% of the exhaust gas treatment apparatuses for removing harmful substances, SO.sub.2, Nox and like is carried out by a wet-type means and the adsorbents are quick lime, gypsum and the like. However, these adsorbents are washed, i.e. so-called treatment with water.
Other than the above-mentioned methods, dry type treatments using coal ash, lime and gypsum are available.
The treatments as mentioned above have the following problems. Those apparatuses are large in size, complicated and the mechanism is of a large scale.
Even in case of dry type treatments, conventional apparatuses have separately a desulfurization tower and a denitration tower, or require a step comprising mixing different components, kneading and solidifying the mixture with water and shaping by drying.
In a wet type apparatus there are provided separately a dust removing tower and an absorbing tower, and the exhaust gas is washed with a water shower and the waste water is subjected to a water treatment. The dry type treatment using coal ash, lime and gypsum also costs, as much as, the wet type treatment.
The present invention has been made in view of the problems of the conventional treating techniques.